feat: add activity cli

[scotwells]

Registers the new activity CLI so users can query the platform for activity logs. Also adds documentation for the activity logs to provide guidance on how to query audit logs.

Note

I'd love feedback around how we want to organize documentation for this project moving forward. It seems like it would be helpful to organize the documentation similar to how we organize the commands. Thinking documentation could be grouped into folders when there's multiple commands within a group that are related to each other.

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Relates to datum-cloud/enhancements#536

[gianarb]

Great work, I am not sure how the documentation pipeline works overall and how the documentations coming from the various projects are being merged together but for maintainability I feel like we should try to sneak all the per command documentation into cobra and I think we should build (during release maybe) and validate (in ci/cd) a markdown version for it

https://github.com/spf13/cobra/blob/main/site/content/docgen/md.md

other than we can also generate the man pages and use it if we decide to do distro and package distribution.

To me having some part of the documentation generated from the cobra commands sounds great because we have a single source of truth. We can write "different kind of documentation" such as ctl user guide, tips, changelog or whatever as markdown like we do today but the per command one I think should be generated as much as possible.

For what concerns this PR specifically I think it is good to go, and we can discuss further on the documentation elsewhere.

[scotwells]

@gianarb good idea on being able to generate reference CLI documentation from the cobra commands directly! Agree on there being a difference between user guides and command reference documentation.

Maybe user/reference would be a good location for auto-generated documentation and then user/guides would be more guide focused documentation. Something we can play with!